1. Field of the Invention
The present invention relates to a stator.
Priority is claimed on Japanese Patent Application No. 2005-336783, filed Nov. 22, 2005, the content of which is incorporated herein by reference.
2. Description of Related Art
There is known a three-phase motor that drives a rotor in three phases (namely, U-phase, V-phase, W-phase) with a stator wound with coils of each phase that traverse the circumference in a wave shape by weaving between adjacent teeth (see, for example, Japanese Unexamined Patent Application, First Publication No. 2002-165396).
It is possible to constitute a stator for a three-phase motor in which loop windings of two phases having a mutual phase difference of, for example, 60 or 240 electrical degrees are connected in a V-shape and energized by sine waves with a mutual phase difference of 120 electrical degrees. Such a stator can serve as one capable of generating a rotating magnetic field similarly to a stator of a three-phase motor according to the aforementioned prior art, in which the coils of the U, V, and W-phases are connected in a Y-shape and energized by sine waves with a mutual phase difference of 120 electrical degrees. In the stator, in the case of the loop windings of two phases being short-pitch wave windings displaced 120 electrical degrees, the number of phases of the loop windings mounted in the slots between stator teeth that are adjacent in the circumferential direction is one or two, and thus non-uniform. For this reason, by setting the interval between adjacent teeth in the circumferential direction so as to be non-uniform, a reduction in the winding wire space factor in accordance with the number of phases of the loop windings mounted on the slots can be prevented.
However, setting the interval between adjacent teeth in the circumferential direction so as to be non-uniform causes deviations in the phase difference in the loop windings of two phases, thereby causing deviations in the phases of each phase current. For this reason, in ordinary vector control presupposing the current phase difference between each phase current to be 2π/3=120 electrical degrees, appropriate current control becomes difficult.